6.12-stable review patch. If anyone has any objections, please let me know.
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From: Anderson Nascimento anderson@allelesecurity.com
[ Upstream commit 2e7bba08923ebc675b1f0e0e0959e68e53047838 ]
A NULL pointer dereference can occur in tcp_ao_finish_connect() during a connect() system call on a socket with a TCP-AO key added and TCP_REPAIR enabled.
The function is called with skb being NULL and attempts to dereference it on tcp_hdr(skb)->seq without a prior skb validation.
Fix this by checking if skb is NULL before dereferencing it.
The commentary is taken from bpf_skops_established(), which is also called in the same flow. Unlike the function being patched, bpf_skops_established() validates the skb before dereferencing it.
int main(void){ struct sockaddr_in sockaddr; struct tcp_ao_add tcp_ao; int sk; int one = 1;
memset(&sockaddr,'\0',sizeof(sockaddr)); memset(&tcp_ao,'\0',sizeof(tcp_ao));
sk = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
sockaddr.sin_family = AF_INET;
memcpy(tcp_ao.alg_name,"cmac(aes128)",12); memcpy(tcp_ao.key,"ABCDEFGHABCDEFGH",16); tcp_ao.keylen = 16;
memcpy(&tcp_ao.addr,&sockaddr,sizeof(sockaddr));
setsockopt(sk, IPPROTO_TCP, TCP_AO_ADD_KEY, &tcp_ao, sizeof(tcp_ao)); setsockopt(sk, IPPROTO_TCP, TCP_REPAIR, &one, sizeof(one));
sockaddr.sin_family = AF_INET; sockaddr.sin_port = htobe16(123);
inet_aton("127.0.0.1", &sockaddr.sin_addr);
connect(sk,(struct sockaddr *)&sockaddr,sizeof(sockaddr));
return 0; }
$ gcc tcp-ao-nullptr.c -o tcp-ao-nullptr -Wall $ unshare -Urn
BUG: kernel NULL pointer dereference, address: 00000000000000b6 PGD 1f648d067 P4D 1f648d067 PUD 1982e8067 PMD 0 Oops: Oops: 0000 [#1] SMP NOPTI Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 11/12/2020 RIP: 0010:tcp_ao_finish_connect (net/ipv4/tcp_ao.c:1182)
Fixes: 7c2ffaf21bd6 ("net/tcp: Calculate TCP-AO traffic keys") Signed-off-by: Anderson Nascimento anderson@allelesecurity.com Reviewed-by: Dmitry Safonov 0x7f454c46@gmail.com Reviewed-by: Eric Dumazet edumazet@google.com Link: https://patch.msgid.link/20250911230743.2551-3-anderson@allelesecurity.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/ipv4/tcp_ao.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/net/ipv4/tcp_ao.c b/net/ipv4/tcp_ao.c index bbb8d5f0eae7d..3338b6cc85c48 100644 --- a/net/ipv4/tcp_ao.c +++ b/net/ipv4/tcp_ao.c @@ -1178,7 +1178,9 @@ void tcp_ao_finish_connect(struct sock *sk, struct sk_buff *skb) if (!ao) return;
- WRITE_ONCE(ao->risn, tcp_hdr(skb)->seq); + /* sk with TCP_REPAIR_ON does not have skb in tcp_finish_connect */ + if (skb) + WRITE_ONCE(ao->risn, tcp_hdr(skb)->seq); ao->rcv_sne = 0;
hlist_for_each_entry_rcu(key, &ao->head, node, lockdep_sock_is_held(sk))